Brake operating mechanism



May 27, 1958 J. G. lNGREs BRAKE OPERATING MECHANI SM 3 Sheets-Sheet lFiled Aug. 3, 1955 ATTORNEY May Z7, 1958 J. G. INGRES 2,836,265

BRAKE OPERATING MECHANISM Filed Aug. 3, 1955 3 Sheets-Sheet 2 INVENTOR./EA /v/vo 7' 6. /fve E55 ATTORNEY May 27, 1958 J. G. lNGREs BRAKEOPERATING MECHANISM Filed Aug. 3, 1953 3 Sheets-Sheet 3 ATTORNEY UniteStates Patent F BRAKE OPERATING NmCnANrsM Jeannot G. Ingres, Dearborn,Mich., asrsignor to Kelsey- Thisinvention relates to a brake operatingmechanism for motor vehicle brakes.

Booster brakes for motor vehicles have come into relatively common use,and such mechanisms include a booster motor energizable by movement ofthe brake pedal and the braking forces transmitted to the brakes arepartly foot-generated forces and partly booster motor forces, the twocombining to provide for maximum brake application with a greatlyreduced effort on the part of the vehicle operator.

These mechanisms have been brought to a high state of perfection andseldom fail, although there is always the possibility of a failure inthe source of power for the booster motor, or in the connections betweensuch source and the booster motor. In the event of such failure, mostbooster brake mechanisms now in common use provide for the manualbraking of the vehicle, but the relatively low leverage provided in thelow treadles Which are coming into common use for operating boostermechanisms, requires the exertion of very great clfort on the part ofthe operator, with the application of `braking forces substantiallybelow maximum.

An important object of the present invention is to provide a brakeoperating mechanism, particularly for use in operating a brake boostermechanism, wherein a low pedal is provided for operation of the boostermechanism and wherein the pedal automatically moves to a higher positionand changes the lever ratio of the brake pedal when no power isavailable for the booster, thus giving the operator the substantialleverage necessary for manually applying the brakes to stop the vehicle.

A further object is to provide such a mechanism wherein the pedal andassociated elements are maintained in a normal operating position by adevice operable by power from the same source as that connected to thebooster mechanism, and wherein the pedal and associated parts are biasedto movement to different positions, to automatically move to suchpositions upon a failure of the power source of the booster, to providethe operator with a relatively greater leverage for the manualapplication of the brakes.

A further object is to provide such a mechanism wherein the biasingmeans which operates automatically upon a failure in the booster powermotor includes a lever device for shifting certain elements of the pedalmechanism to manual brake-operating positions and lock ing the parts insuch positions until the source of power for the lbooster mechanismagain becomes operative.

A further object is to provide a mechanism of this character wherein acam device is operative by the means for biasing the parts to manualbrake-operating positions and wherein the cam means is engageable by aroller associated with the biasing means and wherein the roller movespast a given center to positively prevent return movement of the pedaloperated parts to normal positions until the power source becomesavailable `for operating the booster motor.

2,835,265 Patented May 27 195,8v

Other objects and advantages of the invention will become apparentduring the course of the following description.

In the drawings I have shown one embodiment of the invention. In thisshowing:

Figure l is a side elevation of the operating parts of the pedalmechanism shown in position with respect to certain parts of a motorvehicle, parts being shown in section;

Figure 2 is a plan view of the device and associated motor vehicleparts;

Figure 3 is a section taken substantially on line 3 3 of Figure l,portions of the brake pedal lever being Ibroken away and parts beingshown in elevation;

Figure 4 is a section on line 4 4 of Figure 3, with the parts shown insolidv lines with the brake pedal in manually operable position; and

Figure 5 is al diagrammatic representation of the present constructionwith relation to its connection with a brake booster mechanism.

Referring to Figures 1, 2, and 3, the numeral 1t) desig nates a portionof a motor Vehicle frame to the top flange of which a bearing 11 isbolted or otherwise secured as at 12. A shaft 13 is mounted in thebearing 11 and has a reduced end 14- mounted in the upper end of a leverarm 15 and preferably welded thereto as at 16. Intermediate its ends,and offset downwardly from the shaft 13, is a second shaft 17 having areduced end 18 projecting through the lever arm 15 and preferably weidedthereto as at 19.

A sleeve 22 is mounted on the shaft i7 for rocking movement thereon andis reduced in diameter as at 23 for insertion through a lever indicatedas a whole by the numeral 24, this lever being welded to the sleeve 22as at 25.

The lever 24 has an upper arm 26 and a lower arm 27, the former of whichcurves rearwardly as at 28 and is provided at its rear end with aconventional pedal pad 29. The arm 26, accordingly, comprises a pedallever and the portion 28 of the arm projects through an opening 31 inthe vehicle toe board 32, the lower extremity of which merges into thefloor board 33.

The lever end 27 is pivotally connected as at 35 (Figures 1 and 5) to arod 36 extending rearwardly into a booster motor 37. Rearwardly of thismotor is arranged the usual master cylinder 38 having a hydraulic line39 leading therefrom for connection with the vehicle brakes. The rod 36,in accordance with conventional practice, energizes the motor 37 toboost the power generated by the operators foot in applying the brakes,and the parts within the motor 37 are biased to the normal olipositions. For the purpose of illustration, a spring 4d is shown inFigure 5 as the means for biasing the operating rod 36 to the normal offposition shown in such figure.

The booster motor is shown as being of the vacuum operated type and toone side of the motor is connected a vacuum line 44 leading to theintake manifold of the engine or any other source of vacuum. The line 4dis provided with a branch line 45 for a purpose to be described.

The lever arm i5 has its forward edge forming a cam surface 48, asclearly shown in Figure 4, and the lower extremity of this surfaceterminates in an arcuate seat 49 for a purpose to be described. Thelever arm i5 is provided below the axis of the shaft 17 with adownwardly and rearwardly inclined arm 563 arranged parallel to thelever arm 27 as shown in Figure 3. The lower extremity of the arm 5d isprovided with a laterally extending lug 51 normally lying against theforward edge of the lever arm 27, as showny in Figure l. A torsionspring 54 surrounds the sleeve 22. One end 55 of this the rearedge oftheY lever arm ,27,

to .turn the'rle'verY 24j counterclockwise and ',the'rleverl clockwise,thus biasing the lug' 51 into' engagementwith From thef foregoing, itwill be apparentthatin the normal manualY operation Yof the brake lever24, this lever" and the lever 15 turn as a unit upondepression of thepedal 29 to move the rod 36 rearwardly. This rod is biased forwardlybyfthe'iusual biasing means of .the booster motor, shown in thisinstance as the spring .40 (Figure V). Forward movement of the rod 36isY limited by a kstoprscrewuSt carried by Va bracket 595whichY may. bewelded to theframe 10.V Y 1 Y j VReferring to Figuiresfl andAfthenumeral 62 designates a` small vacuum motor as a whole comprising upperand lower- Vcasing sectionsV 63 and 64 between which is clamped'aflexible diaphragm 65,urge'd upwardlyibry a spring 66 and providedVwithl a vertically extending Vstern 67. The 'lower casing section`64isfprovided with an angleV nipple 68 to which ,the branchvacuum line 45is connected. Accordingly, it willl be apparent thatV so long as vacuumis available forpthe booster motor, diferential pressures in theydiaphragm motor Y62A will holdV the diaphragm 65 downwardly. A stubshaft 72 issuitably connected to the web of the frame 10, for examplebyY welding .(not shown) and lsupports a sleeve73 having forward andrear lever arms 74 and 75 projecting therey from. v Y

V'The lever Varm 74 is pivotally connected as at 76 to aV yoke'77'connected to and projecting upwardly from the.

in the plane of the lever 15, as shown inFigure 2, andY supportedby apivot pin S1. This roller, in the off positions of the parts as shown insolid lines in Figure l, is Upon down` slightly` spaced from, the camedge 48.V ward rocking movement of the lever arm 75 as described Ybelow, the roller 80 will engage the cam surface 48,

swingtthe lever Y1,5 rearwardly to the solid linerposition" shownin'Figure Land come to rest against the shoulder 49. VAt such point, theaxis of the pin 81 willrlie slightly below a planepassing through theaxes of theV shafts 17 and 72. Y K n Y t Operation Assuming that themotor vehicle engine is operating,n 5'5 thus providing a source ofpartial vacuum'through the lines 44 and 45, or assuming that some othersource ofVV partial vacuum is in operation, the parts of the apparatusVwill Voccupy the normal off brakepositions shown in VVsolid .linesinFigure l and in Figure 5. Atmospheric Vpressure'infthe diaphragm motorcasingV sectiony 63 will hold the diaphragm 65 downwardly against thecompression of the spring 66, andthe roller 80 will remain'stationary inthe position shown in Vsolid`lines in Figure l and will be inoperative.

Y The operator mayV apply the is particularly intended `for use with a'booster motor brakes by depressing'the pedal pad 29 in the usualmanner.YThe present device y arm 26 for engagement with the rear edge thereof,while Vthe lower Vend 56 of the spring 54 engages against the rear faceof the lug 5,}... This.y spring exerts forces at its ends tending edgeof the lever arm 27, engaging the lug 51, will roel:V the'lever 15 aboutthe axis of the ,shaft 13. In other words, the levers and 24 will berelatively immovableV and rock as a unit about the axis of the shaft13a.Y

In this operation it will be apparent that the upper effective pedallever arm will be represented by the dismoves the rod'36 rearwardly tooperate the valves of the booster motor -37, whereuponithis Vmotor comesinto operation to assist the operator in displacing'lluid from themaster cylinder 38 into the brake line 39.Y ln re'- 'leasing the brakes,the levers 15 and 24 will againrock as a unit about the axisof the shaft13 until theyreach the normal olf positions shown in solid lines inFigure 1. i

Assuming that the sourcefof power fails, for example, f

if the line 44 is broken or if the vehicle is moving with' a dead motor,there will be no vacuum present for op V erating the booster motor, andsince it necessarily follows that there will be no vacuum inthe casingsection 64 of the diaphragm motor, the spring 66 will pushpthe diaphragm65 to the upper position shown in Figure-f4.

. In so operating, the vacuum motor will rock the lever arms 74 and 75in `a clockwise direction as seen in AFigwherein `the booster performsYa Vsubstantial part of the work and, accordingly, it is practical touse a low pedal as suggestedrby the solid line position of the pedalYpad 29m Figure Yl. This greatlyVV facilitates transferring the foot fromthe accelerator treadle to the pedal padV 29, and this pad maybe pushedforwardly and downwardly to apply thebrakes. This action rocks the lever24 as .Y awh'ole,inracounterclockwise direction, and the rear Thus, withthe brake operating parts,

36, their normal oi positions, the axis of the `shaft`17Y ure 1. Theroller 80jengages the cam surface 48V of the lever.` 15, and asthe'roller moves downwardly over such cam surface, it will swing thelever 15 to the Vbrokj` en line position in Figure 1 and the solid lineposition in Figure 4. Referring tothe latter figure, it will be notedthat the roller 80 will come to rest against the shoulder 49, at whichpoint the axis of theshaft 81 of therroller 80 will lie below a planepassing through ythe axesof the shafts 17 and Y72. This movement of thelever 15 is? Yeffect-ed against the tension of the torsion spring 54,and.

the lug 51 will be moved to the broken :line positionVVV inciudig themarwill be moved rearwardly, and the pedal arms 26 Yand 28 andV pedal pad29 will'be moved to theV broken line posi n tions shown in Figure l andthe solid line positions in Y Figure 4. The shaft 17 now becomes astationaryV pivot Y support for the brake lever 24. YVTheupper pedal armwill now belrepresented bythe dist-ance between the axis? of the shaft17 and the point of contact of the'fo'ot on the pedal pad 29, while thelower leverV arm will be rep- K resented by the distance between theaxis ofthe shaft 17 and the axis of the pivot pin 35. ,'Thus, with therod 36 and the elements operated thereby in the 'normal -oif brakepositions, the pedal pad -29 willbe movedV substantially rearwardly.Moreover, the upper pedal leverV arm willbe substantially lengthened andthe lowerarm substantially shortened, thus providing the operator with'Aincreased leverage for the application of the vehicle brakes inthesamemanner as is now accomplished witlrA out the use of a boostermotor.

In this connection attention is invited to the fact that most boostermotors now in actual use are manually op-V `Verable Yin the event'of afailure 'inpower inthel motor, and such a construction Yisnow socorni-nonV in the 'indus-"- try'thatspecilcillustration is unnecessary.'The amountV 'of change in the'. leverage ratios between manualr andpower operation of the brakes, .of course, is Vamatterof;

assenso pedal pad travel from the solid line position in Figure l isapproximately 3 while the pedal pad travel from the broken line positionin Figure 1, upon a failure in power, is vapproximately 51/2".Accordingly, the pedal travel in the foot application of the brakes isnearly twice as great as in power operation of the brakes, and the leverratio is approximately proportionally inceased. This lever ratio, asstated, is `a matter of design. For example, the axes of the shafts and17, if arranged a greater 7istance apart, will increase the ratio forfoot operation, and it the distance between the axes of these shafts isreduced, the leverage ratio increase will be reduced. The pedal leverratios will be a matter of choice or preference on the part ot motorvehicle manufacturers.

-From the foregoing it will be apparent that the present constructionprovides a brake operating means which permits the use of a conventionalbooster brake mechanism with a low pedal. At the same time, iteliminates the necessity for the exertion of great force on the part ofthe operator, in the event no power is available for operating thebooster motor, the change-over in lever ratios upon a failure in powerbeing fully automatic. it also will be apparent that when operativenessof the source of booster motor power is restored, the motor d2, whichmay be of any type responsive to such power, will result in restoringthe parts to their normal positions. Under such conditions, the leverarms 74 and '75 will be rocked counterclockwise to disengage the rollerSQ from the cam surface 48, whereby the force of the torsion spring willrestore the levers and 24 to their normal relative positions shown insolid lines in Figure l.

l claim:

l. A braise operating mechanism comprising a lever structure having apedal arm and a brake operating arm, means providing la normal pivotaxis for said lever structure, power means having mechanical engagementwith said first named means for changing said pivot axis to increase theeffective length of said pedal arm, and means controlling energizationot said power means.

2. A brake operating mechanism comprising a lever structure having afirst lever member and a second 1ever member the former of which ispivoted to said second lever member for turning movement on apredetermined axis intermediate the ends of said first lever member, oneend of said rst lever member constituting a pedal arm and the other endconstituting ya brake operating arm, means independent ot' said lirstlever pivotally supporting said second lever member for rocking movementon an am's parallel to said rst axis and 'between such axis and the endof said pedal arm, means normally connecting said lever members forrocking movement as a unit about said second axis, and means forswinging said second lever member about its pivot axis and disconnectingit from said rst lever member whereby the latter is rree to turn on saidfirst pivot axis independently of said second lever member.

3. A brake operating mechanism comprising a lever structure having alirst lever member and a second lever member the former of which ispivoted to said second lever member for turning movement on apredetermined axis intermediate the ends of said first lever member, oneend of said lirst lever member constituting a pedal arm and the otherend constituting a brake operating arm, means pivotally supporting saidsecond lever member for rocking movement on an axis parallel to saidrirst axis and between such axis and the end of said pedal arm, meansnormally connecting said lever members for rocking movement as a unitabout said second axis, biasing means tending to turn said second levermember about its pivot axis and to disconnect it from said nrst levermember whereby the latter is free to turn on said lirstnamed pivot axisindependently of said second lever member, land means normallyovercoming said biasing means.

4, A braise operating mechanism comprising a iirst lever member havingAan upper end provided with a pedal pad, a brake operating memberconnected to the lower end of said tirst lever member, a second levermember, a first pivot means carried by said second lever member 'andpivotally supporting said iirst lever member intermediate its ends, asecond pivot means for supporting said second lever member for turningmovement `on an axis above the axis ot said rst pivot means, means'biasing said lever members for relative turning movement with respect toeach other, said lever members having interengaging portions limitingsaid relative turning movement to establish normal positions of saidlever members relative to each other, whereupon, upon rocking movementot said first lever member, said lever members will turn as a unit onthe axis of said second pivot means to impart movement to said brakeoperating member, and means for swinging said second lever member tomove the rst pivot means and to disengage said lever members from eachother whereby said lirst lever member is free to turn on the axis of therst pivot means independently of said second lever member.

5. A brake operating mechanism comprising 'a pedal lever having upperand lower ends the former of which is provided with ya pedal pad, asupporting lever mounted for turning movement on a xed axis, meansconnecting said pedal lever for pivotal movement on said su,- portinglever about a second axis below said fixed axis, said levers havingportions interengaging, whereby operation of said pedal lever throughsaid pedal pad will elect movement of said supporting lever `to turnsaid levers as a unit about said iixed axis, means biasing said leversfor relative turning movement to maintain the interengagement betweensaid levers, a brake operating member connected to said lower end ofsaid pedal lever, means limiting movement or" said brake operatingmember to a normal off position from which position it is movable uponoperation of said pedal lever, and means for turning said supportinglever about said lixed axis against said biasing means to disengage theinterengaging portions of said levers and to move said second axis,whereupon said pedal lever is free to roclt on said second axisindependently of said supporting lever.

6. A lbrake operating mechanism in accordance with claim 5 wherein saidlast name-d means comprises a biasing spring, and power means normallyovercoming said spring to render said last named means inoperative.

7. A brake operating mechanism comprising a supporting lever having anupper and lower end, pivot means supporting said lever for turningmovement on a first axis adjacent its upper end, a second pivot meanscarried by said supporting lever at a point spaced below said lirstaxis, a pedal lever mounted intermediate its ends `on said second pivotmeans for turning movement on a second axis, said pedal lever having anupper end provided with a pedal pad and having a lower end below saidsecond axis, a brake operating member connected to such lower end, saidlower lever end being movable rearwardly upon forward movement of saidpedal pad, a stop member carried by said supporting lever and engagingsaid lower lever arm rearwardly thereof, and below said second axis,means biasing said levers for relative turning movement to maintain saidstop mem- -ber in engagement with said lower lever arm, means Lmitingforward movement of said lower lever arm to an oilt position, springmeans for urging said lower lever arm to said normal oli position, andmeans for swinging the lower end of said supporting lever rearwardly toeiect relative turning movement of said levers about said second axisagainst said biasing means and to move said second axis rearwardly andto move said stop member out of engagement with said pedal lever wherebythe latter is free to turn about said second axis independentlyy of saidsupporting lever.

8. A mechanism constructed in accordance with claim 7 wherein the meansfor turning said levers against said biasing means comprises a .devi-ce,engageable with said supporting lever toteiect such turning movement, abiasing spring urging said device to effect suchturning of said levers,and means normally overcoming such biasing spring to maintain saiddevice inoperative.

9. Inpcombination with a brake booster mechanism having an operatingrod, means for biasing said rod to a normal off position, powertransmission means for connecting said booster mechanism to a source ofpower, arlever structure having a pedal arm and a brake operating armconnected to said rod, means' providing a normal pivot laxis forsaidtlever structure intermediate the ends thereof, and means subjecttoa failure of power in said power transmission means for changing saidpivot axis to increase the eective'length yof said pedal arm.

1,0. In combination with a brake booster mechanism having anY operatingrod, means for biasing said .rodV to a normal oft position, means forconnecting said booster mechanism tota source of poweig'a leverstructure having a tirst 'Y lever member and aV second lever member theformer of which is pivoted to saidrsecond ylever member for turningmovement on a predetermined axis intermediate the ends of said firstlever member, one end of said first lever member constituting a pedalarm and the other end constituting a brake operating arm pivotallyconnected to said rod, means pivotally supporting said second levermember for rocking movement on an axis parallel to said first-named axisand between such axis andthe end of said pedal arm, means normallyconnectingpsaid lever members for rocking Vmovement as a unit about saidsecond-named axis, and means for swinging said second lever about saidsecond-named axis and disconnecting it from said first-named leverwhereby the latter is free' to turn on said rst-named axis independentlyof said second lever member, said last-named means being operative bylafailure of'power in said source.

ll. In combination with a brake booster mechanism having anoperatingrod, means for biasing said rodto a normal od' position, andmeans for connecting'said booster mechanism to Va source of power, alever structure having a rst lever member and a'second lever member theformer of which is pivoted to said second lever member for turningV,movement on a predetermined Vaxis intermediate the ends 'of said irstlever member, fone end of said iirst lever member constituting a pedalarm tending to turn said second lever about said second-namedV pivotaxis and to disconnect it from'said lirst lever member whereby thelatter is free to turn on said first-named pivot axis independently ofVsaid second lever ymeans,-

and means operative by power in said source mally overcoming saidbiasing means. Y

l2. A combination with a differential fluid for norpressure t operatedbooster brake mechanism having a conduit for connectingtit with a sourceof pressure differential, an

operating rod,rmeans for biasing said rod toa normalY of saidfirst-named lever member, both lever members will turn as a unit on saidsecond pivot means to impart Y movementv to said rod, and. meansoperative upon a failure of powerjin said conduit for swinging saidsecond lever member to`move saidriirst pivot means anddisengage saidlever members from each other whereby said first lever member is ,freeto turn on said first pivot means independently of said second levermember.V

13. The combination'delined in claim l?.` wherein said s l5. Acombination with a differential uid pressureV Y operated booster brakemechanism having a conduit for offV position, and means for limitingmovement of'said Y rod to such position, the first lever` member havingan upper end provided with a pedal pad, a second'lever member, a iirstpivot means carried by said second lever member and pivotally supportingsaid tirst lever member intermediate its ends, a second pivot means forsup- Y portinggsaid second lever member for turning movement on an axisabove the axis of said first pivot means, means biasing said levermembers for relative turning movement with respect to each other, saidlever members having' interengaging portions limiting said`relative'turning movement to establish normal positions of said levermembers relativeV to each other, whereby, upon rocking movementconnecting it with a source of pressure differential, VanV operatingrod, means for biasing said rodtto a normal off position, and means forlimiting movement of said rodr to such position, a supporting leverhaving'an upper end, pivot means supporting said lever for turningmovement on a xed axisV adjacent its upper end, Va second pivot meanscarried by said supporting lever at a point spaced below said fixedaxis, a pedal lever pivotallyV supported intermediate its ends on-saidsecond pivot means, said pedal lever having an upper end provided with apedal pad and having a lower end pivotallyV connectedV to said rod, astop member carried by said supporting lever and engaging said lowerpedal lever end rearwardly thereof below the axis of said second pivotmeans, means baising Ysaid stop member into engagement with said lowerlever end, and means operative upon a failurefof power in said conduitfor swinging the lower end ofrsaid supporting lever rearwardly Vto etectrelative turnin'gimovement of said levers about the axis of said secondpivot means Y and against said biasing means and to move said secondrearwardly, and a power Vdevice operative by differential' pressure insaid conduit for overcoming said second biasing means. i

l7.,A brakeV operating mechanism comprising aitsupporting lever havingan upper end, pivot means supporting said lever for turning movement ona tirst axis adjacent its upper end, a second pivot meansy carried bysaid supporting lever at a point spaced below said first axis, a

pedal lever mounted intermediate its ends on said Vsecond pivot meansfor turning movement on a second axis, said pedal leverthaving an upperend provided with a pedal pad and having a lowerV end below saidsecond'axis, a brake operating member connected to such lower end, saidlower lever end being movable rearwardly upon forward movement of saidpedal pad, a stop member carried by said supporting lever and engagingsaid lower Y lever end rearwardly thereof, and below saidv secondV axis,means biasing said levers for relative turning movement to maintainVsaid stop member in engagement withsaid e lower lever end, meanslimiting forward movement of said lower lever end to an olii' position,spring means for Yurging said lower lever end .to said normal offposition, Y the forward edge of said supporting lever constituting aYcam surface terminating at'its lowertextremitytin` a .stop shoulder, acontrol lever having an end movable between an upper inoperativeposition disengaged from said supporting lever and a lower positionengaging said stop shoulder and operative upon movement to said lowerposition for swinging said supporting lever rearwardly to move saidsecond pivot means rearwardly and move said stop member out ofengagement with said pedal lever whereby the latter is free to turnabout said second pivot means independently of said supporting lever,spring means urging said end of said control lever to its lowerposition, and power means normally operable for maintaining said end ofsaid control lever in its upper position.

18. A mechanism according to claim 17 provided with a third pivot meanssupporting said control lever, the point of engagement of said controllever with said supporting Y lever, when said supporting lever is inengagement with said stop shoulder, being below a plane passing throughthe axes of said second and third pivot means.

19. An operating mechanism for a brake operating rod comprising a firstlever having a pedal pad and a connection with the brake operating rod,a pivot pin supporting said rst lever at a point spaced from said pedalpad and from said connection, a second lever carrying said pivot pin,means spaced from said pivot pin for supporting said second lever forturning movement on a fixed axis, rigid means engaging between saidlevers and tending to prevent relative turning movement therebetweenfrom normal positions relative to each other whereby operation of saidlirst lever by a force applied to said pedal pad will turn said leversas a unit, a control lever normally disengaged from said second leverand engageable with said second lever to turn it about said xed axis tochange the position of said pivot pin and release said levers from eachother whereby said first lever turns about said pivot pin, and means foroperating said control lever to move it into engagement with said secondlever.

20. An operating mechanism for a brake operating rod comprising a rstlever having a pedal pad and a connection With the brake operating rod,a pivot pin supporting said first lever at a point spaced from saidpedal pad and from said connection, a second lever carrying said pivotpin, means spaced from said pivot pin for supporting said second leverfor turning movement on a xed axis, rigid means engaging between saidlevers and tending to prevent relative turning movement therebetweenfrom normal positions relative to each other whereby operation of saidrst lever by a force applied to said pedal pad will turn said levers asa unit, said means comprising an element for limiting turning movementof said second lever in one direction to its normal position relative tosaid irst lever, and a spring biasing said second lever to suchposition, a control lever pivoted for turning movement on a lixed axisand having a roller at one end normally out of engagement with saidsecond lever and engageable with said second lever upon turning movementof said control lever to change the position of said pivot pin andrelease said levers from each other whereby said rst lever turns aboutsaid pivot pin, and means for applying a force to said control lever forturning it to engage said roller with said second lever to turn thelatter about said last-named fixed axis.

i References Cited in the le of this patent UNITED STATES PATENTS1,582,118 Bragg et al Apr. 27, 1926 1,601,649 Schaeffer Sept. 28, 19261,754,387 Hall Apr. 15, 1930 1,954,520 Bragg et al. Apr. 10, 19342,037,869 Wall Apr. 21, 1936 2,265,546 Price Dec. 9, 1941 2,365,960Ingres Dec. 26, 1944 2,596,040 Nutt May 6, 1952 FOREIGN PATENTS 336,696Great Britain Oct. 23, 1930

